Commit f0fb6953 authored by Dominik Brodowski's avatar Dominik Brodowski Committed by Herbert Xu
Browse files

hwrng: core - use per-rng quality value instead of global setting 



The current_quality variable exposed as a module parameter is
fundamentally broken: If it is set at boot time, it is overwritten once
the first hw rng device is loaded; if it is set at runtime, it is
without effect if the hw rng device had its quality value set to 0 (and
no default_quality was set); and if a new rng is selected, it gets
overwritten. Therefore, mark it as obsolete, and replace it by the
per-rng quality setting.

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: default avatarDominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 077bb7a1

drivers/char/hw_random/core.c

+20 −13
Original line number Diff line number Diff line
@@ -44,14 +44,14 @@ static unsigned short default_quality; /* = 0; default to "off" */ 


module_param(current_quality, ushort, 0644);

MODULE_PARM_DESC(current_quality,

		 "current hwrng entropy estimation per 1024 bits of input");

		 "current hwrng entropy estimation per 1024 bits of input -- obsolete");

module_param(default_quality, ushort, 0644);

MODULE_PARM_DESC(default_quality,

		 "default entropy content of hwrng per 1024 bits of input");



static void drop_current_rng(void);

static int hwrng_init(struct hwrng *rng);

static void hwrng_manage_rngd(void);

static void hwrng_manage_rngd(struct hwrng *rng);



static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,

			       int wait);
@@ -160,11 +160,13 @@ static int hwrng_init(struct hwrng *rng) 
	reinit_completion(&rng->cleanup_done);



skip_init:

	current_quality = rng->quality ? : default_quality;

	if (current_quality > 1024)

		current_quality = 1024;

	if (!rng->quality)

		rng->quality = default_quality;

	if (rng->quality > 1024)

		rng->quality = 1024;

	current_quality = rng->quality; /* obsolete */



	hwrng_manage_rngd();

	hwrng_manage_rngd(rng);



	return 0;

}
@@ -429,19 +431,24 @@ static int hwrng_fillfn(void *unused) 
	long rc;



	while (!kthread_should_stop()) {

		unsigned short quality;

		struct hwrng *rng;



		if (!current_quality)

			break;



		rng = get_current_rng();

		if (IS_ERR(rng) || !rng)

			break;

		mutex_lock(&reading_mutex);

		rc = rng_get_data(rng, rng_fillbuf,

				  rng_buffer_size(), 1);

		if (current_quality != rng->quality)

			rng->quality = current_quality; /* obsolete */

		quality = rng->quality;

		mutex_unlock(&reading_mutex);

		put_rng(rng);



		if (!quality)

			break;



		if (rc <= 0) {

			pr_warn("hwrng: no data available\n");

			msleep_interruptible(10000);
@@ -451,7 +458,7 @@ static int hwrng_fillfn(void *unused) 
		/* If we cannot credit at least one bit of entropy,

		 * keep track of the remainder for the next iteration

		 */

		entropy = rc * current_quality * 8 + entropy_credit;

		entropy = rc * quality * 8 + entropy_credit;

		if ((entropy >> 10) == 0)

			entropy_credit = entropy;
@@ -463,14 +470,14 @@ static int hwrng_fillfn(void *unused) 
	return 0;

}



static void hwrng_manage_rngd(void)

static void hwrng_manage_rngd(struct hwrng *rng)

{

	if (WARN_ON(!mutex_is_locked(&rng_mutex)))

		return;



	if (current_quality == 0 && hwrng_fill)

	if (rng->quality == 0 && hwrng_fill)

		kthread_stop(hwrng_fill);

	if (current_quality > 0 && !hwrng_fill) {

	if (rng->quality > 0 && !hwrng_fill) {

		hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");

		if (IS_ERR(hwrng_fill)) {

			pr_err("hwrng_fill thread creation failed\n");